Mat made of glass fibers or polyolefin fibers used as a separator in a lead-acid battery

ABSTRACT

Embodiments of the invention provide methods and apparatuses for enhancing electron flow within a battery, such as a lead-acid battery. In one embodiment, a battery separator may include a conductive surface or layer upon which electrons may flow. The battery separator may include a fiber mat that includes a plurality of electrically insulative fibers. The battery separator may be positioned between electrodes of the battery to electrically insulate the electrodes. The battery separator may also include a conductive material disposed on at least one surface of the fiber mat. The conductive material may contact an electrode of the battery and may have an electrical conductivity that enables electron flow on the surface of the fiber mat.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of pending U.S. application Ser. No.13/445,073 filed Apr. 12, 2012. The entire contents of theabove-identified application are herein incorporated by reference forall purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to battery separators, and morespecifically to battery separators having a conductive layer or surface.

Batteries, such as lead-acid batteries, are commonly used for variouspurposes and in various equipment. For example, a common use oflead-acid batteries is in the automotive industry where the batteriesare used to power a starter motor to rotate an internal combustionengine and initiate operation of an automobile. Other commonapplications of the lead-acid battery in automobiles includes poweringvarious components or equipment, such as CD players, lights, powerterminals, and the like. The use of and dependence on batteries isincreasing in automobiles as such vehicles become less reliant onpetroleum as a means for powering the vehicle and more reliant onalternative energies. Currently, many automobiles are produced that areeither powered entirely on electricity or by a hybrid power, such as acombination of electricity and petroleum. These automobiles often haveincreased electrical current and battery discharge time requirementscompared to other applications. Batteries are also commonly used forvarious other industrial or recreational purposes, such as to powerindustrial equipment, appliances, toys, and the like.

The use of and dependence on batteries will likely continue to increasein the future. As such, there is a continued need for improved means forproviding batteries with expanded power output and/or increased batterylife.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention provide battery separators having anelectrically conductive surface to enhance electron flow on the surfaceor surfaces of the battery separator and thereby extend a battery'slife. According to one embodiment, a lead-acid battery is provided. Thelead-acid battery may include a positive electrode, a negativeelectrode, and a fiber mat positioned between the positive and negativeelectrode and separating the electrodes to electrically insulate theelectrodes. The fiber mat may include a plurality of fibers and aconductive material disposed on at least one of its surfaces. Theconductive material may contact the positive or the negative electrodeand may have an electrical resistant of less than about 100,000 ohms persquare to enable electron flow on the surface of the fiber mat.

In one embodiment, the conductive material may have an electricalresistant of less than about 50,000 ohms per square. According toseveral embodiments, the conductive material may comprise severalconfigurations including: a conductive material coating applied to theat least one surface of the fiber mat, a conductive fiber mat positionedadjacent the at least one surface of the fiber mat, a plurality ofconductive polymers interwoven within the fiber mat and/or positionedatop the mat, and the like. The fiber mat may also include an additionalconductive material disposed on the other surface of the fiber mat sothat both the positive and negative electrodes contact one of therespective conductive materials.

According to another embodiment, a battery separator is provided. Thebattery separator may include a mat that includes a plurality ofelectrically insulative fibers. The mat may be configured to separateelectrodes of a battery to electrically insulate the electrodes. Aconductive material may be disposed on at least one surface of the matand may contact one of the electrodes of the battery. The conductivematerial may enable electron flow on the surface of the mat.

The battery separator may also include a microporous membrane disposedon a surface opposite the conductive material. In one embodiment, asecond mat may be disposed on a surface of the microporous membraneopposite the first mat so that the microporous membrane is sandwichedbetween the mats. A second conductive material may be disposed on anouter surface of the second mat so such that the second conductivematerial contacts a second electrode of the battery. Similar to thefirst mat, the second conductive material may have an electricalconductivity that enables electron flow on the surface of the secondmat.

In some embodiments, the first and/or conductive material may include:conductive polymers, nanocarbons, a metal, copper, titanium, vanadium,graphite, graphene, and the like. In one embodiment, the mat is a glassmat and the conductive material is a coating applied to the glass mat.The coating may include a mixture of a binder and the conductivematerial. In another embodiment, the mat is a glass mat and theconductive material is a second mat that includes a plurality ofconductive fibers where the second mat is positioned adjacent the mat.

According to another embodiment, a nonwoven fiber mat having aconductive surface is provided. The nonwoven fiber mat includes aplurality of entangled fibers that form the nonwoven fiber mat, a binderthat facilitates in coupling the plurality of entangled fibers, and alayer of conductive material disposed on at least one surface of theplurality of entangled fibers. The conductive material has an electricalconductivity sufficient to provide the conductive surface of thenonwoven glass fiber mat.

According to another embodiment, a method of providing a batteryseparator having a conductive surface is provided. The method mayinclude providing a fiber mat comprising a plurality of electricallyinsulative fibers and applying a conductive material to at least onesurface of the fiber mat. The conductive material may form a conductivelayer on the surface of the fiber mat and the conductive layer may havean electrical conductivity that enables electron flow on the surface ofthe fiber mat. In one embodiment, the conductive material may have anelectrical resistance of less than about 100,000 ohms per square whilein another embodiment the conductive material has an electricalresistance of less than about 50,000 ohms per square.

The method may also include positioning the battery separator between apositive electrode and a negative electrode of a battery so that theconductive layer contacts one of the electrodes to enhance electron flowwith respect to the contacted electrode. In one embodiment, the step ofapplying the conductive material to the at least one surface of thefiber mat includes applying a coating of conductive material to theplurality of fibers. The coating of conductive material may include abinder mixed with the conductive material. The fiber mat may besaturated with the binder and/or the binder may be sprayed atop the atleast one surface of the fiber mat. In another embodiment, the step ofapplying the conductive material to the at least one surface of thefiber mat includes positioning a second fiber mat adjacent the surfaceof the fiber mat. The second fiber mat may include a plurality ofconductive fibers and/or a plurality of fibers coated with a conductivematerial.

The method may further include positioning a microporous membrane on anopposite surface of the fiber mat. The method may additionally includepositioning a positive electrode conductor adjacent a surface of apositive electrode and positioning the battery separator adjacent thepositive electrode so that the conductive layer contacts the positiveelectrode. The positive electrode may be disposed between the fiber matand the positive electrode conductor so that electrons at a first regionof the positive electrode flow along the conductive layer of the fibermat to a positive terminal of the battery when the conductive layerprovides an electrical path of minimal resistance at the first region.Electrons at a second region of the positive electrode may flow alongthe positive electrode conductor to the positive terminal of the batterywhen the positive electrode conductor provides an electrical path ofminimal resistance at the second region.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described in conjunction withthe appended figures:

FIG. 1 illustrates a cross section view of a battery cell havingpositive and negative electrodes separated by a battery separatorincluding a conductive surface or layer according to an embodiment ofthe invention.

FIG. 2 illustrates a cross section view of another battery cell havingpositive and negative electrodes separated by a battery separatorincluding a conductive surface or layer according to another embodimentof the invention.

FIG. 3 illustrates a perspective view of a battery separator having aconductive layer or surface according to an embodiment of the invention.

FIG. 4 illustrates an expanded cross section view of a battery cellhaving a battery separator including a conductive surface or layeraccording to an embodiment of the invention.

FIG. 5 illustrates a method of providing a battery separator having aconductive surface or layer according to an embodiment of the invention.

In the appended figures, similar components and/or features may have thesame numerical reference label. Further, various components of the sametype may be distinguished by following the reference label by a letterthat distinguishes among the similar components and/or features. If onlythe first numerical reference label is used in the specification, thedescription is applicable to any one of the similar components and/orfeatures having the same first numerical reference label irrespective ofthe letter suffix.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention provide battery separators having anelectrically conductive surface to enhance electron flow on the surfaceor surfaces of the battery separator and thereby extend a battery'slife. The battery separators described herein may be especially usefulfor prolonging the life of lead acid batteries where continual dischargeof the battery results in degradation of the battery's electrodes. Forexample, during discharge of the lead acid battery, lead dioxide (a goodconductor) in the positive electrode plate is converted to lead sulfate,which is generally an insulator. The lead sulfate can form an imperviouslayer or layers encapsulating the lead dioxide particles, which maylimit the utilization of the lead dioxide, and thus the battery, to lessthan 50 percent of capacity, and in some cases about 30 percent. Theinsulative lead sulfate layer may also lead to higher resistance for thebattery. The effect may be a decrease in the electrical current providedby the battery and/or in the discharge life of the battery.

The electrically conductive battery separator may improve or extend thelife of the lead acid battery by improving electron flow or currentwithin the battery. In some embodiments, an electrically conductivesurface of the battery separator provides an additional route for theelectrons to flow (i.e., an additional current route), the additionalroute being separate from the route provided by the conductor plate orgrid of the battery. In other embodiments, electrons may flow on theelectrically conductive surface of the battery separator or on theconductor plate or grid depending on which conductor provides the routeor path of minimal resistance to battery terminal. In this manner, asthe electrodes continually degrade due to formation of lead sulfate, theroute or path of the electrons through the electrode and/or along thebattery separator surface can adjust to compensate for the degradation.

The battery separator may include a fiber mat including a plurality ofelectrically insulative fibers. The fiber mat may have an electricalresistance greater than about 1 million ohms per square. The fiber matmay be a nonwoven porous mat where the plurality of fibers are entangledand/or coupled by a binder. In one embodiment, the fiber mat includesglass fibers, polyolefin fibers, polyester fibers, and the like. Theglass, polyolefin, or polyester fiber mat may provide a reinforcementlayer for the battery separator. The battery separator may also includea micoporous membrane or polymeric film positioned adjacent one surfaceof the fiber mat. The microporous membrane may include pores sizedsmaller than the fiber mat. The battery separator may prevent physicalcontact between positive and negative electrodes of the battery whileenabling free ionic transport across the mat.

Positioned on a surface of the fiber mat opposite the microporousmembrane may be an electrically conductive material that provides thefiber mat with an electrically conductive surface. The battery separatormay be positioned within the battery so that the electrically conductivematerial/layer contacts one or more of the battery's electrodes. In someembodiments, the electrically conductive material includes a layer ormat of conductive fibers or a layer of other conductive materials, suchas a metallic sheet or film. In other embodiments, the conductivematerial may include a coating of conductive material applied to or atopthe fiber mat. In a specific embodiment, the conductive material isadded to a binder material that is applied to the plurality of fibersduring manufacture of the fiber mat or sprayed atop a previouslymanufactured fiber mat.

The electrically conductive layer of the fiber mat may be disposedacross substantially the entire surface of the fiber mat so that theelectrically conductive layer is substantially equivalent in size andshape to the fiber mat. In this manner the electrically conductive layerprovides a large conductive surface that contacts the electrode andalong which electrons may flow. The large conductive surface alsoprovides virtually limitless paths or routes along which the electronsmay flow as insulative lead sulfate is produced through repeated chargeand discharge of the battery.

In some embodiments, the battery separator includes a conductivematerial or layer on both surfaces so that both the positive andnegative electrodes of the battery contact a conductive surface of thebattery separator. Having generally described several embodiments of theinventions, additional aspects of embodiments of the invention will berecognized with reference to the figures.

FIG. 1 illustrates a cross section of a cell 100 of a lead-acid battery.In one embodiments, the lead-acid battery may include 3 such cells 100connected in series to provide about 6.3 volts. In another embodiment,the lead-acid battery may include 6 such cells 100 connected in seriesto provide about 12.6 volts. In still other embodiments the lead-acidbattery may include more or less cells depending on the voltage needed.

Cell 100 includes a positive electrode 102 and a negative electrode 112.Positive electrode 102 includes a positive electrode conductor 106, suchas a metal grid or plate, having a coating of positive active material,such as lead dioxide 104. Conductor 106 is electrically coupled with apositive terminal 108. Similarly, negative electrode 112 includes anegative electrode conductor 116, such as a metal grid or plate, havinga coating of negative active material, such as lead 114. Conductor 116is electrically coupled with a negative terminal 118. Positive electrode102 and negative electrode 112 are immersed in an electrolyte (notshown) that may include sulfuric acid and water.

Separating positive electrode 102 and negative electrode 112 is batteryseparator 120. Battery separator 120 prevents physical contact ofpositive electrode 102 and negative electrode 112 while enabling ionictransport across battery separator 120, thus completing a circuit andallowing an electronic current to flow between positive terminal 108 andnegative terminal 118.

Battery separator 120 include a porous fiber mat 122 that includes aplurality of electrically insulative fibers, such as glass, polyolefin,polyester, and the like. In one embodiment, fiber mat 122 is essentiallynon-conductive having an electrical resistance greater than about 1Megohm per square. The low conductance of the fiber mat 122 electricallyseparates positive electrode 102 and negative electrode 112, or in otherwords prevents or minimizes an electronic current from passing betweenpositive electrode 102 and negative electrode 112 and thereby shortingthe circuit. In one embodiment, fiber mat 122 includes glass,polyolefin, or polyester fibers, or any combination thereof, that arecoupled together via a binder. Glass, polyolefin, or polyester fiber mat122 may be manufactured by removing (e.g., via a vacuum) liquid from asuspension of the fibers in the liquid medium. The binder is thenapplied to the wet-laid non-woven glass or polyolefin fibers to formfiber mat 122. In one embodiment, fiber mat 122 may have a thickness ofbetween about 50 micrometers and about 500 micrometers, a porosity ofbetween about 50 percent and about 90 percent, and have an average poresize of between about 5 micrometers and about 5 millimeters.

In other embodiments, the fibers of fiber mat 122 may include inorganicceramics, or various polymers, such as polyvinylidene fluoride,polytetrafluoroethylene, polyamide, polyvinyl chloride, polyester,nylon, polyethylene terephthalate, and the like.

Positioned on one side of fiber mat 122 may be a conductive layer 124formed by applying a conductive material to the surface of fiber mat122. In the embodiment shown in FIG. 1, conductive layer 124 ispositioned facing positive electrode 102, although in other embodimentsconductive layer 124 may face negative electrode 112. The conductivematerial, and thus conductive layer 124 or surface of fiber mat 122,contact positive electrode 102, or more specifically the positive activematerial (e.g., lead dioxide 104) of positive electrode 102. Theconductive material and/or conductive layer 124 has an electricalresistance of less than about 100,000 ohms per square and more commonlyless than about 50,000 ohms per square so as to enable or enhanceelectron flow on the surface of the fiber mat 122. In some embodiments,conductive layer 124 may be electrically coupled with positive terminal108 (or negative terminal 118 when positioned facing negative electrode112) so as to provide a route or path for an electronic current to flowbetween positive electrode 102 (or negative electrode 112) and positiveterminal 108 (or negative terminal 118) and/or a conductive elementelectrically coupled therewith. In other embodiments, electrons may flowalong either fiber mat 122 or positive electrode conductor 106 dependingon which conductive surface provides an electrical path of minimalresistance. For example, electrons proximate to positive terminal 108may flow along an electrical path of the positive electrode conductor106 while electrons distal to positive terminal 108 may flow along anelectrical path of fiber mat 122 due to increase lead sulfate buildingon the positive electrode conductor 106 adjacent that location.

In one embodiment, conductive layer 124 is formed on the surface offiber mat 122 by coating the conductive material onto fiber mat 122 orspraying the conductive material on the surface of fiber mat 122. Forexample, the conductive material may be added to a primary bindermaterial that is applied to the wet-laid non-woven fibers to couple thefibers together. The primary binder/conductive material mixture andwet-laid non-woven fibers may then be cured so that the conductivematerial completely coats or is saturated throughout fiber mat 122 toform conductive layer 124. In another embodiment, fiber mat 122 may bemanufactured in a standard process where a primary binder without theconductive material is applied to the wet-laid non-woven fibers tocouple the fibers together. The conductive material may then bedispersed in a secondary or dilute binder that is then coated or sprayedonto the surface of fiber mat 122. Fiber mat 122 may then be cured sothat the conductive material forms conductive layer 124 across a definedportion or the entire surface of fiber mat 122. In this embodiment, amajority of the conductive material may lay or be positioned atop thesurface of fiber mat 122.

In another embodiment, a fiber mat 122 may be manufactured according toknown process. A catalyst may be subsequently added to a surface offiber mat 122 and metal ions, such as copper, may be grown on thesurface of the fiber mat via the applied catalyst. In still anotherembodiment, the conductive material of conductive layer 124 may be addedto fiber mat 122 via chemical vapor deposition processes.

In lead-acid battery environments, the conductive material used shouldbe relatively corrosion resistant due to the aggressive electrochemicalenvironment of the battery. In some embodiments, the conductive materialmay include a metal, a nanocarbon, graphene, graphite, a conductivepolymer (e.g., polyanilines), nanocarbons or carbon nanotubes, copper,titanium oxides, vanadium oxides, tin oxides, and the like. In aspecific embodiment, the conductive material include carbonnano-platelets, such as graphene. The graphene may be added to theprimary binder or secondary/dilute binder as described above and appliedto fiber mat 122 (e.g., a glass or polyolefin fiber mat) between about0.5% and 50% by weight, or in some embodiments between about 1% and 10%by weight. When cured, the coating of graphene forms conductive layer124 across a defined portion or the entire surface of fiber mat 122.

In another embodiment, conductive layer 124 comprises a conductive fibermat, foil, or screen that is positioned adjacent the surface of fibermat 122. In one embodiment, the conductive fiber mat may be made bycoating the conductive material onto fiber mat 122 or spraying theconductive material on the surface of fiber mat 122. The foil or screenmay include a metal, one or more conductive polymers, and the like. Theconductive fiber mat may include a plurality of conductive fibersarranged in a non-woven or woven pattern and coupled together via abinder. The conductive fiber mat may be coupled with fiber mat 122 via abinder and the like. Electrons may flow along the conductive fiber mat,foil, or screen as described herein, such as up to the positive and/ornegative terminal or through lead dioxide 104 and/or lead 114. Asdescribed above, the conductive material of the conductive fiber mat,foil, or screen may include a metal, a nanocarbon, graphene, graphite, aconductive polymer (e.g., polyanilines), nanocarbons or carbonnanotubes, copper, titanium oxides, vanadium oxides, tin oxides, and thelike.

Positioned on the opposite side of fiber mat 122 is a microporousmembrane, such as a polymeric film 126 or an AGM (Absorbent Glass Mat).The polymeric film may be positioned adjacent negative electrode 112 andmay include micro-sized voids that allow ionic transport (i.e.,transport of ionic charge carriers) across battery separator 120. In oneembodiment, microporous membrane or polymeric film 126 may have athickness of 50 micrometers or less, and preferably 25 micrometers orless, may have a porosity of about 50% or 40% or less, and may have anaverage pore size of 5 micrometers or less and preferably 1 micrometeror less. Polymeric film 126 may include various types of polymersincluding polyolefins, polyvinylidene fluoride, polytetrafluoroethylene,polyamide, polyvinyl alcohol, polyester, polyvinyl chloride, nylon,polyethylene terephthalate, and the like.

Referring now to FIG. 2, illustrated is a cross section of anotherembodiment of a cell 200 having a positive electrode 202 and a negativeelectrode 212 separated by battery separator 220. Similar to cell 100,positive electrode 202 includes a positive electrode conductor 206, apositive active material, such as lead dioxide 204, and a positiveterminal 208. Likewise, negative electrode 212 includes a negativeelectrode conductor 216, a negative active material, such as lead 214,and a negative terminal 218. Battery separator 220 includes amicroporous membrane 222, such as the microporous membrane describedabove (e.g., a polymeric film). In some embodiments, element 222represents a fiber mat (e.g., AGM or polyolefin mat) that does not havea conductive layer or surface. The glass/polyolefin mat or microporousmembrane 222 has a negligible conductance (e.g., resistance of 1 Megohmper square or greater) such that electrons do not flow or transferacross the glass/polyolefin mat or microporous membrane 222. Positionedon each side of the microporous membrane 222 is a fiber mat, 230 and 240respectively, such that microporous membrane (or alternatively aglass/polyolefin mat) 222 is sandwiched between the two fiber mats.Fiber mats 230 and 240 may include similar fiber materials, such asglass or polyolefin, or different fiber materials. Each fiber mat, 230and 240, may be conductive or include a conductive layer, 232 and 242respectively, so that both the negative electrode 212 and positiveelectrode 202 contact a conductive layer or surface of a respectivefiber mat. As described herein, electrons may flow along or with respectto the conductive layers or surfaces, 232 and 242, of the fiber mats,230 and 240 respectively. In another embodiment, only one of the fibermats, 230 and 240, may be conductive or include a conductive layer. Forexample, both fiber mats, 230 and 240, may be glass or polyolefin fibermats, but only fiber mat 240 that contacts positive electrode 202 mayinclude a conductive layer 242.

Conductive layer 232 and 242 may include similar conductive materialsand layers, such as graphene or another material coated onto or appliedto the fiber mats, fiber mats made of conductive fibers, and the like,or may include different conductive materials and layers, such as onemat having a conductive coating while the other mat has conductivefibers; or both mats including dissimilar coating or conductive fibers.

In another embodiment, a single fiber mat may include conductive layerson both sides or surfaces of the fiber mat so that both the positiveelectrode and the negative electrode contact conductive material of oneof the respective conductive layers of the single fiber mat.

Referring now to FIG. 3, illustrated is a perspective view of a nonwovenfiber mat 300 having a conductive surface 304 along or upon whichelectrons can flow. A portion of the conductive surface 304 is cut awayto reveal a plurality of entangled fibers 302 (e.g., glass fibers) thatmay be coupled together with a binder to form the nonwoven fiber mat300. Conductive surface 304 may be a coating of conductive material or aseparate mat, film, or screen positioned adjacent a surface of theplurality of entangled fibers 302. Although conductive surface 304 isshown in FIG. 3 as a solid surface or sheet, it should be realized thatconductive surface 304 may be a coating on individual fibers (e.g.,glass fibers) of fiber mat 300.

In one embodiment, a conductive material (e.g., graphene) is mixed witha primary binder or secondary binder and applied to the plurality ofentangled fibers 302 during manufacture of the fiber mat 302 orsubsequent thereto. In another embodiment, a conductive fiber matincludes a plurality of entangled conductive fibers coupled together viaa binder. Conductive surface 304 may have an electrical resistance ofless than about 100,000 ohms per square, and more commonly less thanabout 50,000 ohms per square, to enable electron flow on the conductivesurface 304 of fiber mat 300.

Referring now to FIG. 4, illustrated is an enlarged cross section of acell 400 of a battery, such as a lead-acid battery. Cell 400 includes apositive electrode conductor 404 electrically coupled with a positiveterminal 406. Conductor 404 may have a coating of a positive activematerial, such as lead dioxide 402. Positioned adjacent the lead dioxide402 material is a fiber mat 410 have a conductive surface 412 asdescribed above (e.g., a coating, conductive fiber mat, and the like).Cell 400 is immersed in an electrolyte (not shown) and undergoes anelectrochemical reaction as a current flow from positive terminal 406 toa negative terminal (not shown). As the electrochemical reaction takesplace, lead dioxide 402 is converted into lead sulfate 420 and electronsget generated in layer 402. Lead sulfate 420 is generally an insulatorand can form an impervious layer encapsulating lead dioxide 402particles, which may limit the utilization of the lead dioxide 402.Further, lead sulfate 420 may also result in higher resistance withinthe battery resulting in decreased electron flow through the positiveelectrode (e.g., through lead dioxide material 402 and conductor 404)and, thus, reduce current from positive electrode 406 to the negativeelectrode. For example, lead sulfate 420 can increase the resistance ofconductor 404 so that electrons flowing from a bottom region ofconductor 404 experience increased resistance. Conductive surface 412may provide an alternate route or path of less resistance along whichthe electrons can flow.

Electrons that are produced in lead dioxide 402 around the path 430B canflow to the conductive surface 412 of fiber mat 410 when the resistancebetween lead dioxide 402 and positive terminal 406 via conductor 404increases due to the formation of lead sulfate 420. Alternatively, at adifferent location the resistance between lead dioxide 402 and positiveterminal 406 via conductor 404 may be lower than the resistance ofconductive surface 412. Thus, path 430A may represent electrons flowingto conductor 404 when lead sulfate 420 develops at a point nearconductive surface 412. In this manner, electrons may flow througheither or both conductive surface 412 and conductor 404 depending onwhich conductive material provides the least electrically resistivepath. Further, electrons may flow virtually anywhere along conductivesurface 412 so that when lead sulfate forms in one region or area, theelectrons are able to flow around that region.

For simplicity, cell 400 only shows the positive electrode, although itshould be realized that above description may equally apply to thenegative electrode.

Referring now to FIG. 5, illustrated is a method for enhancing orproviding electron flow on a surface of a battery separator. At block510, a fiber mat or battery separator comprising a fiber mat isprovided. The fiber mat may include a plurality of fibers (e.g., glassfibers and the like) and may have an electrical resistance of greaterthan about 1 million ohms per square as described above. At block 520, aconductive material is applied to at least one surface of the fiber mat.The conductive material may have an electrical resistance of less thanabout 100,000 ohms per square, and more commonly less than about 50,000ohms per square, and may be applied so that the conductive materialforms a conductive layer on the surface of the fiber mat. The conductivelayer may enhance electron flow on the surface of the fiber mat. Atblock 530, a polymeric film or microporous membrane, such as thosedescribed above, may be positioned on an opposite surface of the fibermat (i.e., on a surface opposite the surface the conductive material isapplied to). At block 540, the fiber mat (i.e., the battery separator)may be positioned between a positive electrode and a negative electrodeof a battery so that the conductive layer contacts one of the electrodesto enhance electron flow with respect to the contacted electrode and/orwithin the battery.

In one embodiment, applying the conductive material to the surface ofthe fiber mat may include applying a coating of conductive material tothe plurality of fibers of the fiber mat. The coating of conductivematerial may include a binder mixed with the conductive material. Thefiber mat may be saturated with the binder, such as during manufactureof the fiber mat, and/or the binder may be sprayed or applied atop thesurface of the fiber mat. In another embodiment, applying the conductivematerial to the surface of the fiber mat may include positioning asecond fiber mat adjacent the surface of the fiber mat, the second fibermat including a plurality of conductive fibers or a plurality of fiberscoated with a conductive material so that the second fiber mat iselectrically conductive.

The method may also include positioning a positive electrode conductoradjacent a surface of a positive electrode of a battery and positioningthe fiber mat (i.e., battery separator) adjacent the positive electrodeso that the conductive layer contacts the positive electrode and so thatthe positive electrode is disposed between the fiber mat and thepositive electrode conductor. The electrons at a first region of thepositive electrode may flow along the conductive layer of the fiber matto a positive terminal of the battery because the conductive layerprovides an electrical path of minimal resistance at the first regionwhen compared with an electrical path of the positive electrodeconductor at the first region. Likewise, electrons at a second region ofthe positive electrode may flow along the positive electrode conductorto the positive terminal of the battery because the positive electrodeconductor provides an electrical path of minimal resistance at thesecond region when compared with an electrical path of the conductivelayer at the second region.

A test was performed using a standard battery separator (i.e., a batteryseparator without a conductive layer) and a battery separator describedherein having a conductive layer or surface. The test showedimprovements in battery life of batteries using the battery separatorhaving a conductive layer or surface. The test was performed as follows:Batteries were constructed having two electrodes, a polymeric filmmembrane, and a glass fiber mat—1 battery included a glass fiber matwithout a conductive surface and 2 of the batteries included a glassfiber mat with a conductive surface. A Proam universal AC-DC adaptor wasset at 2.4V and allowed to charge the battery for about 1 hour. Thecurrent was recorded. A Multiplex multi-charger LN-5014 was allowed todischarge the battery completely. The charge and discharge steps wererepeated for additional cycles. The current-time curve was integrated todetermine the capacity (in milliamp-hours).

As mentioned above, two battery separators types were used: a firstglass fiber mat battery separator without a conductive surface, and asecond glass fiber mat battery separator having the fiber mat coatedwith Graphene. The glass fiber mats were positioned to contact thepositive electrode so that the conductive surface of the second glassfiber mat contacted the positive electrode. Three batteries were tested:1 battery having a separator without a conductive surface and 2batteries having separators with conductive surfaces. Each battery wastested for 5 charge and discharge cycles. The results of the test areshown in the table below.

Calculated capacity Time Average % Type (mAH) (min) capacity/minImprovement Standard battery mat 407.6 60.07 5.90 +/− 0.58 NA 366.8360.03 347.9 60.03 328.02 60.03 321.22 60.03 Standard battery mat 40660.07 6.30 +/− 0.35 6.7% coated w/Graphene 369.3 60.1 (Run 1) 381.860.05 356 60.07 Standard battery mat 419.6 60 6.31 +/− 0.55 7.0% coatedw/Graphene 396.9 60.02 (Run 2) 387.1 60.02 349.1 59.98 341.1 60

As shown in the table, approximately a 7% improvement was observed inthe batteries using separators that include the conductive surface orlayer. This 7% improvement was observed after just 5 charge/dischargecycles. This preliminary results suggest the possibility of increasingbattery cycle life by using battery separators including or having aconductive surface or layer, such as those described herein.

The fiber mats and/or battery separators described herein may generallybe referred to as non-conductive mats or mats having neglibigleconductance, non-appreciable conductance, minimal conductance, and thelike. It should be realized that non-conductance, negligibleconductance, non-appreciable conductance, and the like may not mean anabsolute lack of conductance per se, but rather may describe an abilityto act or function as an electrical insulator. For example, such mats(i.e., non-conductive, negligibly conductive, non-appreciablyconductive, and the like) may have such small conductivity (i.e., suchhigh electrical resistance) that they may be used as an electricallyinsulative layer between objects, such as battery electrodes, and/or maynot provide any measurable or appreciable conductive values. Put anotherway, such mats may function as and/or measure as an open circuit (i.e.,may measure a roughly infinite resistance).

Having described several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theinvention. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent invention. Accordingly, the above description should not betaken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the device” includesreference to one or more devices and equivalents thereof known to thoseskilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

What is claimed is:
 1. A battery separator comprising: a mat including aplurality of electrically insulative fibers, the mat being configured toseparate a positive electrode and a negative electrode of a battery toelectrically insulate the positive and negative electrodes; a primarybinder that adheres the electrically insulative fibers together, theprimary binder enabling the battery separator to be used in an aqueouselectrolyte environment; and a conductive material disposed on at leastone surface of the mat to form a conductive layer on the at least onesurface of the mat, wherein the conductive material contacts at leastone of the positive or negative electrodes of the battery, and whereinthe conductive material enables electron flow on the surface of the mat;wherein the conductive material is a separate material from an activematerial of the positive electrode and an active material of thenegative electrode; wherein the conductive material is a coating appliedto the plurality of electrically insulative fibers adhered together viathe primary binder, the coating comprising a mixture of the conductivematerial and a secondary binder.
 2. The battery separator of claim 1,further comprising a microporous membrane disposed on the oppositesurface of the mat.
 3. The battery separator of claim 2, furthercomprising: a second mat disposed on an opposite surface of themicroporous membrane such that the microporous membrane is sandwichedbetween the mat and the second mat; and a second conductive materialdisposed on an outer surface of the second mat such that the secondconductive material contacts a second electrode of the battery, thesecond conductive material having an electrical conductivity thatenables electron flow on the surface of the second mat.
 4. The batteryseparator of claim 1, wherein the conductive material comprise one ormore materials selected from the group consisting of: conductivepolymers; nanocarbons; a metal; copper; titanium; vanadium; graphite;and graphene.
 5. The battery separator of claim 1, wherein the matcomprises a glass mat, and wherein the coating is applied to the glassmat.
 6. The battery separator of claim 1, further comprising a secondmat comprising a plurality of conductive fibers, the second mat beingpositioned adjacent the mat.
 7. A nonwoven fiber mat having a conductivesurface, the nonwoven fiber mat comprising: a plurality of entangledfibers that form the nonwoven fiber mat; a primary binder that couplesthe plurality of entangled fibers; and a layer of conductive materialdisposed on at least one surface of the plurality of entangled fibers,the conductive material having an electrical conductivity sufficient toprovide the conductive surface of the nonwoven glass fiber mat; whereinthe conductive material is a separate material from an active materialof a positive electrode and an active material of a negative electrodeof a lead acid battery; and wherein the layer of conductive material isa coating applied to the at least one surface of the plurality ofentangled fibers, the coating comprising a mixture of the conductivematerial and a secondary binder.
 8. The nonwoven fiber mat of claim 7,further comprising a microporous membrane disposed on the oppositesurface of the nonwoven fiber mat.
 9. The nonwoven fiber mat of claim 8,further comprising: a second nonwoven fiber mat disposed on an oppositesurface of the microporous membrane such that the microporous membraneis sandwiched between the nonwoven fiber mat and the second nonwovenfiber mat; and a second conductive material disposed on an outer surfaceof the second nonwoven fiber mat, the second conductive material havingan electrical conductivity that enables electron flow on the surface ofthe second nonwoven fiber mat.
 10. The nonwoven fiber mat of claim 7,wherein the conductive material comprise one or more materials selectedfrom the group consisting of: conductive polymers; nanocarbons; a metal;copper; titanium; vanadium; graphite; and graphene.
 11. The nonwovenfiber mat of claim 7, wherein the nonwoven fiber mat comprises a glassmat, and wherein the coating is applied to the glass mat.
 12. Thenonwoven fiber mat of claim 7, further comprising a second matcomprising a plurality of conductive fibers, the second mat beingpositioned adjacent the nonwoven fiber mat.
 13. A lead-acid batterycomprising: a positive electrode; a negative electrode; and a fiber matseparating the positive electrode and the negative electrode so as toelectrically insulate the positive and negative electrodes, the fibermat comprising: a plurality of fibers; a primary binder that couples theplurality of fibers; and a conductive material disposed on at least onesurface of the fiber mat so as to contact the positive or the negativeelectrode, the conductive material having an electrical resistant lessthan about 100,000 ohms per square so as to enable electron flow on thesurface of the fiber mat wherein the conductive material is a separatematerial from an active material of the positive electrode and an activematerial of the negative electrode; and wherein the conductive materialis a coating applied to the at least one surface of the fiber mat, thecoating comprising a mixture of the conductive material and a secondarybinder.
 14. The lead-acid battery of claim 13, wherein the conductivematerial has an electrical resistant less than about 50,000 ohms persquare.
 15. The lead-acid battery of claim 13, further comprising aconductive fiber mat positioned adjacent the at least one surface of thefiber mat.
 16. The lead-acid battery of claim 15, wherein the conductivefiber mat comprises a plurality of conductive polymers.
 17. Thelead-acid battery of claim 13, further comprising an additionalconductive material disposed on an opposite surface of the fiber mat sothat both the positive and negative electrodes contact one of therespective conductive materials.
 18. The battery separator of claim 1,wherein the secondary binder is a dilute binder.
 19. The nonwoven fibermat of claim 7, wherein the secondary binder is a dilute binder.
 20. Thelead-acid battery of claim 13, wherein the secondary binder is a dilutebinder.